Wingspan 16-18 mm.
With its bright purple and yellow markings, this small species is easily recognisable, but local and scarce.
It was formerly found in various coastal sand-hills in the north and west of England, western Ireland and parts of Scotland. However it has become scarcer in recent years and is now believed extinct in mainland England and Scotland, occurring only in a few locations in Northern Ireland and one locality on the Isle of Man.
The larvae feed internally on wild thyme (Thymus).
There are two generations, flying in June and again in August, when the moths are on the wing in the daytime sunshine as well as at night.